Oilseed rape (Brassica napus) (OSR) is a partly wind-pollinaled crop which has been increasingly cultivated both in Europe and overseas. Allergological data about OSR is scarce and controversial. We evaluated the frequency of sensitizalion to OSR pollen by skin prick test and RAST over a period of 1 yr. Airborne OSR pollen load and the agricullural role of this crop were analysed. Furthermore, six patients were investigated by immunoblot. In 4468 patients with suspect inhalant allergy investigated between June 1994 and May 1995, routine skin prick testing revealed OSR sensitivity in 7.1% ot pollen-allergic patients. In all, monovalent sensitization was detected in nine patients. Routine pollen counts showed daily maxima not exceeding 50 grains/m3/24 h, but airborne OSR pollen has continuously increased during the last decade correlating with the increasing acreage. Characterization of OSR allergens by immunoblol revealed major allergens of 6/8 kD, 12/14 kD and in the high molecular weight range at 33, 42, 51, 58/61 and 70kD. Some OSR proteins may cross-react with birch pollen allergens. In summary, the results suggest that OSR pollen is a moderate but true source of allergy and may sensitize despite low pollen exposure.